The present invention relates to the field of vibratory mechanical energy and more particularly, to energy transmission devices for transmitting vibratory energy that may be used in the construction of ultrasonic motors or the transmission of vibratory energy therefrom.
The prior art designs or ultrasonic motors and acoustical impedance transformers or tools are generally of a nature that the vibratory energy generated is transmitted in a plane substantially along the axis thereof and the shape, length and design, or the various parameters thereof, have become known in the art as to the various dimensional relationships in order to properly transmit vibrations. All of the prior art devices are generally made out of metallic materials for high power applications and in some instances plastic material for low power applications.
Because of the inherent strength limitations of metallic tools, the nodal regions of ultrasonic tools or horns under high stroke conditions tend to crack. I propose a new class of ultrasonic tools, or output sections, which are comprised of composite materials, having the following characteristics:
1. High tensile strength PA1 2. High strength to weight ratios PA1 3. High stiffness fibers PA1 1. Unusual short or long wavelength dimensions for a given frequency. PA1 2. Variations in density of tool. PA1 3. Modification of the nature of output tip portion by differing fiber orientation.
Typical strengths of such fibers can run as high as millions of pounds per square inch and modulii of tens of millions. Graphite fibers, which act as the vibration transmitting components, for example, have tensile strengths on the order of 310 k psi and modulii of 75,000 k psi. Graphite, then, and fibers of sapphire, boron, silicon carbide, are used as a substrate and are impregnated with plastic or metal, one of which acting as coupling means. This gives rise to a situation in which a plurality of fibers, which may be random, oriented, woven, etc., are surrounded with a matrix of metal or plastic and pressed, molded or otherwise formed into the shape of the output section of an ultrasonic transducer or transmission member. A series of advantages are inherent in this design. The uniqueness inheres in the idea of prefabricated ultrasonic tools or devices which formerly were expensive shapes to machine. In the past, cheap prefabrication was impossible because plastic alone is generally too weak to withstand high-stress vibration, ergo molded plastic would not prove useful; alternately cast metals are similar in strength and have poor acoustic properties.
Unique possibilities that are inherent in the design of devices in accordance with the present invention are as follows:
All or the above can be achieved by varying the concentration and orientation of the reinforcing fibers. Of course, the fibers themselves by virtue of their properties will tend to impede the progress of a crack due to stress as such reinforced materials are totally devoid of cracks, such cracks ruin metal tools.
Applicant has now discovered that the fabrication of vibratory ultrasonic composite devices as hereinafter disclosed in detail further expands the utilization and application of mechanical vibrations at an ultrasonic frequency, herein defined to include vibrations in the range of 1,000 to 1 million cycles per second. This advancement in the art permits the design of various ultrasonic transmission assemblies, motor constructions and vibratory members or tools not heretofore possible.